A Westgate inmate who was caught with drugs in his prison cell has appeared in Magistrates' Court.

Jason Wheatley, 27, admitted to possessing 0.17 grams of cannabis, which prison officers found hidden under a drinking cup in his cell.

Wheatley is currently serving a 14-year sentence for possessing $200,000 worth of cannabis and a "mini arsenal" of firearms in his ex-girlfriend's home.

On Friday, Crown counsel Larissa Burgess said Police received a complaint on July 24 that Wheatley had marijuana in his possession.

Prison officers arrived at his cell at 7.50 a.m. and conducted a search, finding a white paper twist containing the drug. Wheatley told them "a guy gave it to me", but wouldn't say who.

He was later officially charged with the offence, to which he replied "it was just a little, I will plead guilty". He will be sentenced tomorrow (Tuesday).